In the building of automotive vehicle tires and the like, it is frequently desirable to prepare by injection molding of an elastomeric material such as rubber, a so-called tread ring or running ring which forms the running surface of the tire and consists of an endless annular layer of rubber bonded to a reinforcement in the form of so-called belts.
It is known to provide, for the production of pneumatic tires without carcasses, an apparatus for the casting or injection molding of rubber upon one or more belts, e.g. as described in Austrian Pat. No. 339,757, using a core and means for forming a mold cavity with the core such that, upon separation of the parts of the mold cavity and removal of the core, the tire structure is obtained.
In this system, the core has upper and lower portions axially movable relative to at least two rows of segments and the latter rows of segments comprise radially movable segments to enable separation of the annular molded body from the mold-form elements.
In Austrian Pat. No. 339,756, the outer shell-forming members of the mold comprise groups of segments swingable about axes and lying on opposite sides of the rubber ring which is to form the tire.
The fabrication of pneumatic tires with carcasses with either of these apparatuses is not convenient since the systems described cannot readily accommodate the belts. Accordingly, a two-stage process must be provided in which the belts are first wound upon a winding drum, are separately injection molded with tread rubber to form an endless layer thereof on the belts and the resulting tread ring must be combined with the remainder of the tire.
Conventional apparatus for this purpose requires complicated manipulation, storage and transportation of the rings and a multiplicity of steps which are seldom sufficiently coordinated to make the process economical.
The molding operations themselves are complicated by the relatively complex mold-forming members as well.